POWER UNIT FOR ARC WELDING MACHINE

摘要

PURPOSE:To ensure the reignition of an arc even when a polarity is reversed from a straight polarity to reverse polarity by providing the switching circuit impressing the charging voltage of a smoothing capacitor on a base metal and welding electrode via the resistance for discharging at the pulse generation time. CONSTITUTION:A constant pulse is generated by a multivibrator 46 at the electrode time when a welding electrode is switched from a straight polarity to reverse polarity. At this pulse generation time a transistor 42 is turned ON, a transistor 44 is further turned ON the charging voltage of a smoothing capacitor 32 is impressed between a welding electrode 7 and base metal 8. Since the charging voltage of the smoothing capacitor 32 is higher than the smoothing output voltage appeared at the output side of a smoothing reactor 12, this higher voltage is impressed between the welding electrode 7 and base metal 8 to perform the reignition of the arc. Namely the arc current is sustained without causing the misfiring of an arc with the charging voltage of the smoothing capacitor impressed as the voltage for reignition between the welding electrode 7 and base metal 8 via a switching circuit at the time when the welding electrode is in the low impedance state of polarity reversing time from a straight polarity to reverse polarity.